High Seroprevalence of Antibodies Against SARS-CoV-2 Among Healthcare Workers 8 Months After the First Wave in Aden, Yemen

Abstract

Background: The true burden of COVID-19 in Yemen is underestimated as testing remains limited. MSF needed to rapidly identify and manage staff illness in the MSF Aden Trauma Centre. In this study we aimed to screen staff, offer PCR testing to symptomatic individuals, and conduct serological rapid tests to determine past infection. Methods: Four months after the peak of the first wave, we offered all the staff at the MSF Aden Trauma Centre PCR if symptomatic, and a baseline SARS-CoV-2 serology screening followed by follow-up screenings. A final round was scheduled four months after the baseline. A rapid serology lateral flow test, NG-Test® IgM-IgG was used in all rounds and in the final round, an electrochemiluminescence immunoassay (ECLIA) (Elecsys® Anti-SARS-CoV-2 assay). Univariate and multivariate analyses were used to identify risk factors for seropositivity. The level of agreement between the different serology assays used was investigated. Findings: Overall 69 out of 356 participants (19.4%, 95% CI 17.9 – 20.8) tested positive by NG-Test® between September and November 2020. A sub-sample of 161 staff was retested in January 2021. Of these, the NG-Test® detected only 13 positive cases, whereas the ECLIA detected 109 positive cases. The adjusted seroprevalence by ECLIA was 59% (95%CI 52.2 – 65.9). Those who were non-medical had significantly lower odds of seropositivity compared to the medical staff (AOR 0.43, 95% CI 0.15 – 0.7, p<0.001). The positive percent agreement between the two tests was very low (11%). Interpretation: Our results suggest a very high SARS-CoV-2 seroprevalence in healthcare workers in Yemen, highlighting the need for regular testing and rapid vaccination of all healthcare workers in the country. Rapid serological tests are likely to under-estimate true infection rates. Funding Information: Medecins Sans Frontieres, Epicentre Declaration of Interests: All authors declare no competing interests. Ethics Approval Statement: Written informed consent was obtained. This protocol was approved by the MSF Ethics Review Board on July 30, 2020, reference number 2056a, and by Aden University Institutional Review Board on August 9, 2020 (Research Code: REC-79-2020).